Research On Thermal-Mechanical Coupling Characteristics And Fatigue Damage Of High-Speed Train Brake Disc Under Wheel-Rail Excitation

Brake disc is one of the most critical components of high-speed train braking system.In recent years,with the increase of train speed,some problems exposed during the operation of brake disc seriously affect the driving safety.The requirements for brake disc are increasingly high,and related research is also closer to the actual situation.Therefore,this paper considers the study of wheel-rail excitation on thermal mechanical coupling characteristics and fatigue of brake disc.The main research contents are as follows:(1)Based on the vehicle system dynamics,the vehicle dynamics model with rigid axle mounted brake disc was established with dynamics software.The stability and critical speed indexes of the model were verified respectively to ensure the reliability and accuracy of the simulation model.Based on this,the vibration data of the brake disc under different wheel polygon order and coupling conditions of wave depth and Wu guang spectrum were calculated respectively.The vibration characteristics of the brake disc in time domain and frequency domain were analyzed.The data with larger vibration acceleration of the brake disc was selected as the vibration excitation of the thermal and mechanical coupling of the brake disc in the following chapter.(2)A three-dimensional transient thermal-mechanical coupling finite element model was established to calculate the thermal-mechanical coupling characteristics of the axle brake disc under emergency braking conditions with different initial braking speeds and braking pressures.Simulation software was used to calculate the temperature field load with friction power method.The influence of wheel-rail and wheel-rail excitation on thermal mechanical coupling of axle brake disc and the distribution of temperature field and thermal stress field are obtained.The causes of multiple friction radii of disc surface,the variation trend of temperature and thermal stress of brake disc with thickness and radial direction were analyzed.The maximum temperature of disc surface varies with braking pressure and initial braking speed and the influence of wheel-rail excitation on the disc.It was found that the temperature of disc surface with wheel-rail excitation is greater than that without wheel-rail excitation.(3)According to the results of thermal and mechanical coupling,a crack was inserted into the highest temperature area of the brake disc surface,and a finite element model of the brake disc with a crack was established.The residual circumferential stress of crack generated by the main brake disc was used to select the appropriate calculation method of stress intensity factor.(4)The fatigue damage and crack initiation life of brake disc under wheel-rail excitation and no wheel-rail excitation were calculated by the coupling effect of temperature field and stress field combined with the fatigue analysis method and S-N curve.Based on the calculation of crack stress intensity factor,the relationship between crack propagation life and crack length under wheel-rail and wheel-rail excitation is analyzed.With the increase of crack length,the crack propagation life becomes smaller.When the crack limit length is reached,the failure of the brake disc occurs.